Two weeks later I'm in another supermarket rifling through the "ripe" avocados. A lady in her 60s is doing the same, and together we lift three pallets containing around 80 packets, all rock-hard, before she gives up with a cry of: "Ripe and ready, indeed!"

And it seems these aren't isolated incidents. When I asked on Twitter if anyone else had been searching in vain, I got a big response. "I've just become accustomed to pre-planning when using the buggers," was one reply, and, "I buy several days in advance and put them in the airing cupboard. Even the ready-to-eat ones!" was another.

Bemoaning the lack of ripe avocados sounds trivial, of course, but it raises a more serious question. A twin pack of "ripe" avocados costs £2 in most supermarkets. "Ripen at home" ones are often — though not always — sold for less (around £1.50 for a four-pack). How are supermarkets able to charge a premium for fruit and veg marketed as ready to eat, when in some cases it isn't?

Unfortunately, consumers don't have many options when "ripe and ready" produce fails to deliver — it's far from confined to avocados. In their respective seasons, I've bought "ripe" pears with the yield of a pebble, and "ripe" mangos and nectarines that are anything but.

"There is no legislation that relates solely to this situation," says David Pickering, food lead officer of the Trading Standards Institute. "The Food Safety Act section 15 relating to misleading descriptions will apply, but we would need to prove beyond all reasonable doubt that the description is misleading." If it doesn't say "guaranteed" on the packet, there's not a lot you can do.

If you've bought the produce and it isn't "ripe and ready" you can approach the store for a refund or replacement. But if there are simply no ripe ones in store that day, then tough cheese. Or, tough avocados.

Given the UK avocado market was reportedly worth £51m in 2012, it's no surprise that all the major supermarkets go to great pains to get their fruit "ripe and ready". Avocados ripen off the tree. They are picked when firm and transported to the UK, kept in climate-controlled temperatures en route. "Avocados are ripened by the suppliers here in the UK," explains an industry insider. "The avocados are in boxes on palettes and warm air gets blown into the spaces between them, evenly warming the fruit and allowing them to ripen quicker." Tesco uses a "bespoke avocado texture analyser" according to a spokesperson, which uses "acoustic testing" to check for ripeness. The suppliers will also test a batch using a penetrometer, and Tesco tests again at its depot. Asda also uses "infra-red to test internal quality" while Sainsbury's uses mature avocados with high oil content and says its Ripe & Ready avocados are "fully ripened in specialist ripening rooms". Waitrose "accurately forecasts future demand" in its battle to get its Perfectly Ripe avos on the shelves.

Meanwhile Asda has introduced new traffic-light packaging for its avocados – green for ripe, orange for "nearly ripe" and pink for "requires a little more time". "The days of avocado guess work will soon be a distant memory!" says Asda's avocado buyer, Damien Gray.

So the mystery of my rock-hard "ripe and ready" avocados remains. The supermarkets have invested in serious kit to get their avos on the shelves in perfect condition, but it seems fruit and veg can't always be coerced into optimum ripeness. Meanwhile, I'm learning to give up on spontaneous avocado buying, settling for hard avocados, and my own DIY ripening room … a brown paper bag containing the avos and a banana. The bananas produce ethylene gas which helps ripen other fruits.

Works every time.

Have you been frustrated by so-called "ripe and ready" produce? Where do you find the best avocados?